At the present time, manufacturers who utilize large presses and dies, such as of the type used for forming large sheet metal body parts for automobiles, have attempted to reduce the press size by replacing conventional low-pressure gas springs (typically air springs) with higher pressure springs which are typically filled with nitrogen. This desire to utilize a high-pressure gas springs is obviously predicated on the fact that such spring can be of significantly smaller size while still providing a large force-absorbing capacity due to the high internal gas pressure which exists in the spring. Such high-pressure gas spring, which has been developed for this purpose, is illustrated in my earlier U.S. Pat. No. 4,664,362.
These high-pressure springs, however, do introduce concerns with respect to the safety of such devices and the safety of operating personnel. This is important both during operation of the spring due to the pressure build up therein during application of impact forces thereto, and also when handling of the spring such as during installation, maintenance or removal. In recognition of this need to provide suitable control valves for providing safety against pressure overload, and at the same time provide convenient and safe procedures for discharging high-pressure fluid from the spring, applicant has developed a valve for such purpose and same is disclosed in applicant's earlier U.S. Pat. No. 4,662,616. Additional improvements in such valve are disclosed in applicant's U.S. Pat. No. 4,721,289. While these latter valves have proven to possess desirable structural and functional characteristics, nevertheless further investigation and study of the installation, handling and use characteristics of gas springs of this general type have resulted in applicant's development of still further improvements in such valves so as to significantly improve the performance characteristics of the valves when utilized on high-pressure springs of this type, while at the same time maintaining or improving the overall safety of such system.
In the improved valve arrangement of the present invention, which valve is preferably positioned within a bore formed in the gas spring housing for controlling flow of pressure fluid both into and out of the pressure chamber, the valve arrangement includes a first one-way check valve means coacting between first and second passages for permitting high-pressure gas to be supplied from the first to the second passage and thence into the pressure chamber, while preventing flow in the opposite direction. The valve arrangement also includes a second flow-control valve means coacting with a third passage for controlling flow of gas through the third passage for discharge from the high-pressure chamber. The valve arrangement preferably includes a removable sleeve-like liner supported within the housing bore, and a control piston sealingly and slidably supported within the liner. The one-check valve means is mounted on the control piston, and the flow control valve means includes an annular valve seat formed on the liner for cooperation with an annular valve element which is fixedly associated with the control piston.
In one embodiment of the invention, the control valve means, when opened, such as for permitting manual discharge of the spring or release of excess pressure, permits the gas to be discharged to an external location such as the surrounding atmosphere.
In a further and preferred embodiment of the invention, the opening of the flow control valve means, such as during a period of excessive pressure, permits the gas in the pressure chamber to flow through the third passage past the opened flow control valve means into a fourth passage, the latter communicating through a further one-way check valve means with the first passage so that the gas is automatically resupplied to the supply line (that is, the first passage). This further one-way check valve means is preferably mounted on and carried by the control piston. This arrangement is particularly desirable since, if any leakage occurs past the flow control valve means, then any leaked gas will ultimately be resupplied to the supply line.
In a variation of the preferred embodiment as described above, the valve arrangement is mounted on the end cap of the gas spring housing and is disposed within a bore which extends through the end cap in axial alignment with the axis of the high-pressure spring. The valve arrangement projects through the end cap into the pressure chamber and is accommodated within the hollow interior of the piston. The end cap has a plurality of supply ports opening radially outwardly from the bore through the surrounding side wall of the end cap at a plurality of circumferentially spaced locations to facilitate connection of a selected one of the supply ports to an external pressure source.
Other objects and purposes of the invention will be apparent to persons familiar with systems of this general type upon reading the following specification and inspecting the accompanying drawings.